Q3 of 84 Page 301

A lens has power 4 D. Find the focal length that lens.

Given Focal length (f) = 4D

P (in diopter) =


⇒ 4 =


⇒


Now 1m = 100cm


⇒ 0.25m = 25cm


Hence the focal length of lens is 25cm.


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A student uses a lens of focal length- 50 cm. What is the nature of the lens and its power?

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